Samsung Galaxy Tab 2 10.1 — Tab 2 10.1 infested with malware, can't remove!

Hi guys,

I recently bought a Tab 2 10.1 from a friend, with the knowledge that it was "full of viruses". Obviously I know viruses are pretty non-existent so assumed just malware. Anyway I booted it up, and it had already just been given a factory reset. After using it for a few minutes it begins to run incredibly slow, and I notice that it is starting to download and install different apps without my consent, anything from "PornClub" and "GoolePlay" (not a typo). I tried to reset it again myself, but after a few minutes it begins downloading and installing things by itself again, and runs unbelievably slow and sometimes has popups that won't get off the screen and it requires me to restart the device. Looking in My Files I can see that there are some questionable folders in the system folders. How can I go about completely wiping this thing and having it fresh again? I'm pretty new to doing this sort of thing, so any help would be appreciated.

Thanks

Ray